Combine ketchup, vinegar, hoisin sauce, and ginger in a bowl.
Start by cutting the onion into wedges and then cut each wedge into equal halves.
Further, in a bowl, add onion, peppers, and pineapple and toss them in oil. Then add steak and toss again. Pour a little sauce and mix well.
Add the vegetables and steak onto the skewers.
Grill or BBQ the kebabs. Turn them occasionally while basting the hoisin mixture.
Once cooked well. Repeat for other skewers.
Transfer them onto a plate.