Let $${\mathbb {K}}={\mathbb {R}},\,{\mathbb {C}}$$
K
=
R
,
C
, the field of reals or complex numbers and $${\mathbb {H}}$$
H
, the skew $${\mathbb {R}}$$
R
-algebra of quaternions. We study the homotopy nilpotency of the loop spaces $$\Omega (G_{n,m}({\mathbb {K}}))$$
Ω
(
G
n
,
m
(
K
)
)
, $$\Omega (F_{n;n_1,\ldots ,n_k}({\mathbb {K}}))$$
Ω
(
F
n
;
n
1
,
…
,
n
k
(
K
)
)
, and $$\Omega (V_{n,m}({\mathbb {K}}))$$
Ω
(
V
n
,
m
(
K
)
)
of Grassmann $$G_{n,m}({\mathbb {K}})$$
G
n
,
m
(
K
)
, flag $$F_{n;n_1,\ldots ,n_k}({\mathbb {K}})$$
F
n
;
n
1
,
…
,
n
k
(
K
)
and Stiefel $$V_{n,m}({\mathbb {K}})$$
V
n
,
m
(
K
)
manifolds. Additionally, homotopy nilpotency classes of p-localized $$\Omega (G^+_{n,m}({\mathbb {K}})_{(p)})$$
Ω
(
G
n
,
m
+
(
K
)
(
p
)
)
and $$\Omega (V_{n,m}({\mathbb {K}})_{(p)})$$
Ω
(
V
n
,
m
(
K
)
(
p
)
)
for certain primes p are estimated, where $$G^+_{n,m}({\mathbb {K}})_{(p)}$$
G
n
,
m
+
(
K
)
(
p
)
is the oriented Grassmann manifolds. Further, the homotopy nilpotency classes of loop spaces of localized homogeneous spaces given as quotients of exceptional Lie groups are investigated as well.