diff --git a/keyboards/handwired/woodpad/rules.mk b/keyboards/handwired/woodpad/rules.mk
index 11f096581..f8c488307 100644
--- a/keyboards/handwired/woodpad/rules.mk
+++ b/keyboards/handwired/woodpad/rules.mk
@@ -71,8 +71,8 @@ RGBLIGHT_ENABLE ?= no
 #    while [ -z $$USB ]; do \
 #      sleep 1; \
 #      ls /dev/tty* > /tmp/2; \
-#      USB=`diff /tmp/1 /tmp/2 | grep -o '/dev/tty.*'`; \
+#      USB=`diff /tmp/1 /tmp/2 | $(GREP) -o '/dev/tty.*'`; \
 #    done; \
 #    avrdude -p $(MCU) -c avr109 -P $$USB -U flash:w:$(BUILD_DIR)/$(TARGET).hex
 #
-#.PHONY: avrdude
\ No newline at end of file
+#.PHONY: avrdude
diff --git a/tmk_core/avr.mk b/tmk_core/avr.mk
index 10b043caa..eb55dba95 100644
--- a/tmk_core/avr.mk
+++ b/tmk_core/avr.mk
@@ -135,13 +135,14 @@ flip: $(BUILD_DIR)/$(TARGET).hex check-size
 	$(BATCHISP) -hardware usb -device $(MCU) -operation start reset 0
 	
 DFU_PROGRAMMER ?= dfu-programmer
+GREP ?= grep
 
 dfu: $(BUILD_DIR)/$(TARGET).hex cpfirmware check-size
 	until $(DFU_PROGRAMMER) $(MCU) get bootloader-version; do\
 		echo "Error: Bootloader not found. Trying again in 5s." ;\
 		sleep 5 ;\
 	done
-	if $(DFU_PROGRAMMER) --version 2>&1 | grep -q 0.7 ; then\
+	if $(DFU_PROGRAMMER) --version 2>&1 | $(GREP) -q 0.7 ; then\
 		$(DFU_PROGRAMMER) $(MCU) erase --force;\
 	else\
 		$(DFU_PROGRAMMER) $(MCU) erase;\
@@ -161,7 +162,7 @@ flip-ee: $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).eep
 	$(REMOVE) $(BUILD_DIR)/$(TARGET)eep.hex
 
 dfu-ee: $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).eep
-	if $(DFU_PROGRAMMER) --version 2>&1 | grep -q 0.7 ; then\
+	if $(DFU_PROGRAMMER) --version 2>&1 | $(GREP) -q 0.7 ; then\
 		$(DFU_PROGRAMMER) $(MCU) flash --eeprom $(BUILD_DIR)/$(TARGET).eep;\
 	else\
 		$(DFU_PROGRAMMER) $(MCU) flash-eeprom $(BUILD_DIR)/$(TARGET).eep;\
@@ -169,7 +170,7 @@ dfu-ee: $(BUILD_DIR)/$(TARGET).hex $(BUILD_DIR)/$(TARGET).eep
 	$(DFU_PROGRAMMER) $(MCU) reset
 
 avrdude: $(BUILD_DIR)/$(TARGET).hex check-size
-	if grep -q -s Microsoft /proc/version; then \
+	if $(GREP) -q -s Microsoft /proc/version; then \
 		echo 'ERROR: AVR flashing cannot be automated within the Windows Subsystem for Linux (WSL) currently. Instead, take the .hex file generated and flash it using AVRDUDE, AVRDUDESS, or XLoader.'; \
 	else \
 		printf "Detecting USB port, reset your controller now."; \
@@ -178,12 +179,12 @@ avrdude: $(BUILD_DIR)/$(TARGET).hex check-size
 			sleep 0.5; \
 			printf "."; \
 			ls /dev/tty* > /tmp/2; \
-			USB=`comm -13 /tmp/1 /tmp/2 | grep -o '/dev/tty.*'`; \
+			USB=`comm -13 /tmp/1 /tmp/2 | $(GREP) -o '/dev/tty.*'`; \
 			mv /tmp/2 /tmp/1; \
 		done; \
 		echo ""; \
 		echo "Detected controller on USB port at $$USB"; \
-		if grep -q -s 'MINGW\|MSYS' /proc/version; then \
+		if $(GREP) -q -s 'MINGW\|MSYS' /proc/version; then \
 			USB=`echo "$$USB" | perl -pne 's/\/dev\/ttyS(\d+)/COM.($$1+1)/e'`; \
 			echo "Remapped MSYS2 USB port to $$USB"; \
 		fi; \
@@ -252,12 +253,12 @@ extcoff: $(BUILD_DIR)/$(TARGET).elf
 bootloader: 
 	make -C lib/lufa/Bootloaders/DFU/ clean
 	echo -e "#ifndef QMK_KEYBOARD\n#define QMK_KEYBOARD\n" > lib/lufa/Bootloaders/DFU/Keyboard.h
-	echo -e `grep "MANUFACTURER" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
-	echo -e `grep "PRODUCT" $(ALL_CONFIGS) -h | tail -1` Bootloader >> lib/lufa/Bootloaders/DFU/Keyboard.h
-	echo -e `grep "QMK_ESC_OUTPUT" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
-	echo -e `grep "QMK_ESC_INPUT" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
-	echo -e `grep "QMK_LED" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
-	echo -e `grep "QMK_SPEAKER" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
+	echo -e `$(GREP) "MANUFACTURER" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
+	echo -e `$(GREP) "PRODUCT" $(ALL_CONFIGS) -h | tail -1` Bootloader >> lib/lufa/Bootloaders/DFU/Keyboard.h
+	echo -e `$(GREP) "QMK_ESC_OUTPUT" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
+	echo -e `$(GREP) "QMK_ESC_INPUT" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
+	echo -e `$(GREP) "QMK_LED" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
+	echo -e `$(GREP) "QMK_SPEAKER" $(ALL_CONFIGS) -h | tail -1` >> lib/lufa/Bootloaders/DFU/Keyboard.h
 	echo -e "\n#endif" >> lib/lufa/Bootloaders/DFU/Keyboard.h
 	make -C lib/lufa/Bootloaders/DFU/
 	echo -e "BootloaderDFU.hex copied to $(TARGET)_bootloader.hex"
diff --git a/tmk_core/rules.mk b/tmk_core/rules.mk
index ff6af4a88..b556c4609 100644
--- a/tmk_core/rules.mk
+++ b/tmk_core/rules.mk
@@ -370,9 +370,9 @@ show_path:
 	@echo SRC=$(SRC)
 	@echo OBJ=$(OBJ)
 
-ifeq ($(CC),avr-gcc)
+ifeq ($(findstring avr-gcc,$(CC)),avr-gcc)
 check-size:
-	$(eval MAX_SIZE=$(shell n=`avr-gcc -E -mmcu=$(MCU) $(CFLAGS) $(OPT_DEFS) tmk_core/common/avr/bootloader_size.c 2> /dev/null | sed -ne '/^#/n;/^AVR_SIZE:/,$${s/^AVR_SIZE: //;p;}'`; echo $$(($$n)) || echo 0))
+	$(eval MAX_SIZE=$(shell n=`$(CC) -E -mmcu=$(MCU) $(CFLAGS) $(OPT_DEFS) tmk_core/common/avr/bootloader_size.c 2> /dev/null | sed -ne '/^#/n;/^AVR_SIZE:/,$${s/^AVR_SIZE: //;p;}'` && echo $$(($$n)) || echo 0))
 	$(eval CURRENT_SIZE=$(shell if [ -f $(BUILD_DIR)/$(TARGET).hex ]; then $(SIZE) --target=$(FORMAT) $(BUILD_DIR)/$(TARGET).hex | $(AWK) 'NR==2 {print $$4}'; else printf 0; fi))
 	if [ $(MAX_SIZE) -gt 0 ] && [ $(CURRENT_SIZE) -gt 0 ]; then \
 		$(SILENT) || printf "$(MSG_CHECK_FILESIZE)" | $(AWK_CMD); \