In a medium bowl, combine tamari, fish sauce, water and pepper. Set aside.
In a large skillet, heat 2 tbsp (30 mL) coconut oil over medium heat. Add beef and cook, stirring, for about 5 minutes or until cooked to desired doneness. Transfer beef and any drippings to the bowl with the tamari mixture and stir to combine.
Return the skillet to medium heat and melt the remaining coconut oil. Add baby bok choy, garlic, red pepper, yellow pepper and onion; cook, stirring often and adding more coconut oil if needed, for about 8 minutes or until vegetables are softened.
Add beef mixture and cook, stirring, for 3 to 4 minutes or until beef is heated through. Turn off heat, add basil and cook, stirring, until basil is wilted.