Heat a cast iron skillet or a frying pan over medium heat. Add the bacon to the pan and cook for 2 minutes on each side or until crispy. Remove the bacon from the pan and set it aside.
Add the diced onion to the pan and stir to combine with the bacon fat. Cook the onions for 4 to 5 minutes, occasionally stirring, until soft and translucent.
Stir in the potatoes and peppers; season with salt and pepper to taste. Add the vegetable oil and cook for 7 to 10 minutes or until the potatoes are fork-tender.
Crumble the bacon and add it to the pan; stir well. Add the eggs and scramble all the ingredients. Let everything cook for 3 to 5 minutes or until the eggs are cooked to your liking. Taste for salt and pepper and adjust. Remove the pan from the heat.
Place the flour tortillas on a flat surface. Spread two tortillas with 3 to 4 tablespoons each of refried beans. Top the same two tortillas with 3 tablespoons each of cheese. Add the scrambled eggs mixture to taste. Top each with an extra tablespoon or two of cheese. Place the remaining tortillas on top.
Wipe the cast iron skillet clean (or pan) and set it over medium heat. Spray it with a little cooking spray. Place one quesadilla in the pan. Let it cook for 2 to 3 minutes or until the bottom is golden and crispy. Flip it over and cook it for 2 to 3 more minutes.
Remove the quesadilla from the heat.
Transfer to a plate, slice each tortilla into 4 wedges and serve with salsa and/or guacamole.